Some more observations...
I remember someone commenting about the spectrum display on the AR-5700D actually being useful and I agree. I spent some time with it and while it is not as pretty as the IC-R8600 one, it works.
I had poor results feeding the IF OUT on the IC-R8600 into a AR-DV1 or the SDRplay for decoding DMR and other digital modes. I think it is due to IF OUT being a regenerated analog signal using a 12-Bit DAC. It is a different story with the 45.05 MHz IF OUT on the AR-5700D. No problem using DSDPlus Fast Lane through a SDRPlay. It would be great if the 12 kHz IF output could be used for decoding more digital modes than just DRM. This would be better than using the IF Out.
The AR-Alpha and AR-5700D have Audio IQ (AIQ) to provide output for DRM. The advantage of the IC-R8600 is audio over USB. The AIQ output on the AR-5700D is the analog line output, so I had to use my iMic USB Audio dongle. SDRSharp and SDRuno also has Audio IQ output, so I can use Virtual Audio Cable. I had to make sure to turn off the automatic mode change in the SDRSharp Bandplan Plug-in for raw mode to stick after a frequency change.
There does not seem to be many programs that support AIQ input. I tried Sigmira 1r13 even though it is not actively developed. While the raw mode of SDRSharp centers the output around zero, the AIQ output of the AR-5700D is centered on 12 kHz. This causes an interesting spectrum display in Sigmira using 30 KHz Bandwidth as the signal crosses zero and gets cut off at about -3 kHz. It stays near zero up to -8.5 kHz, then there is an image. Setting the Bandwidth lower narrows the cutoff closer to 12 kHz.
One minor problem is zero is always in the center of the Sigmira spectrum when using IQ so I had to set the frequency width to 50 kHz. Everything worked fine by just remembering to center the signal at 12 kHz. I was able to sync and have a high FEC level on an encrypted STANAG 4285 signal I suspect is CFH. I tried Multipsk and got the same type of spectrum display, but it was not obvious if it was decoding anything. I find the Multipsk interface too busy. I used Dream DRM set to positive IQ input and synced on several DRM signals, but they were too weak to decode audio.
I did come across a bug with AIQ. I did something so AIQ was just regular line out while tuning around HF. I tried a number of things, including resetting the receiver, and it did not work. I tuned in the local weather on 162 MHz in FM and then switched to AIQ, it worked. If AIQ is not working you get the spectrum above zero mirrored below zero.
Accessory Socket 1 has changed from my other AOR Receivers. I used the Detector Output (Pin 2) in the past on my AR-5000, AR-Alpha, and AR-8600 for digital decoding. It is good to see it is still available for NFM mode on the AR-5700D. They changed the Audio Input (Pin 3) on some receivers to a mute input and the high level audio output (Pin 6) to a GPS time pulse input. There is a stereo line out jack for high level audio.
The swap of the antenna port supporting HF when using I/Q Out is annoying. I played around with SDRSharp on HF and wondered how WBCQ got on 6906 kHz. It turned out the spectrum display was inverted. If I shifted the frequency up, then the spectrum would move to the right, and the frequency ribbon would move to the left. I selected Invert Spectrum in the AOR Settings and then it worked correctly. I then found I needed to select Invert Spectrum below 25 MHz and deselect Invert Spectrum at 25 MHz and above.
I noticed the Auto setting of the Attenuator in the SDRSharp AOR control panel did not seem to work. It was set to Auto with the preamp on. I went to Manual and turned the preamp off. It remained off when I went back to Auto, but I returned it to Manual. It was interesting with the preamp on as I got normal signals when tuned to WWV at 10 MHz, but the noise floor went up and I heard audio from multiple stations when I tuned to a nearby station on 31 Meters. The noise floor went down to normal when I turned off the preamp. I kinda expected this since I am using a Wellbrook Loop and the output is strong. 10 MHz is likely a bandpass filter switch point and there was a strong signal in the passband of the filter used for 31 Meters.
I need to study the SDRsharp Big Book 2024 for more information on the Plugins. Unfortunately it does not cover the changes to support the AOR receivers. More experimentation!